Building a Details View

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The media browsing interface classes provided by the v17 leanback support library include classes for displaying additional information about a media item, such as a description or reviews, and for taking action on that item, such as purchasing it or playing its content.

This lesson discusses how to create a presenter class for media item details, and how to extend the DetailsFragment class to implement a details view for a media item when it is selected by a user.

Note: The implementation example shown here uses an additional activity to contain the DetailsFragment. However, it is possible to avoid creating a second activity by replacing the current BrowseFragment with a DetailsFragment within the same activity using fragment transactions. For more information on using fragment transactions, see the Building a Dynamic UI with Fragments training.

Build a Details Presenter

In the media browsing framework provided by the leanback library, you use presenter objects to control the display of data on screen, including media item details. The framework provides the AbstractDetailsDescriptionPresenter class for this purpose, which is a nearly complete implementation of the presenter for media item details. All you have to do is implement the onBindDescription() method to bind the view fields to your data objects, as shown in the following code sample: 

public class DetailsDescriptionPresenter
        extends AbstractDetailsDescriptionPresenter {

    @Override
    protected void onBindDescription(ViewHolder viewHolder, Object itemData) {
        MyMediaItemDetails details = (MyMediaItemDetails) itemData;
        // In a production app, the itemData object contains the information
        // needed to display details for the media item:
        // viewHolder.getTitle().setText(details.getShortTitle());

        // Here we provide static data for testing purposes:
        viewHolder.getTitle().setText(itemData.toString());
        viewHolder.getSubtitle().setText("2014   Drama   TV-14");
        viewHolder.getBody().setText("Lorem ipsum dolor sit amet, consectetur "
                + "adipisicing elit, sed do eiusmod tempor incididunt ut labore "
                + " et dolore magna aliqua. Ut enim ad minim veniam, quis "
                + "nostrud exercitation ullamco laboris nisi ut aliquip ex ea "
                + "commodo consequat.");
    }
}

Extend the Details Fragment

When using the DetailsFragment class for displaying your media item details, extend that class to provide additional content such as a preview image and actions for the media item. You can also provide additional content, such as a list of related media items.

The following example code demonstrates how to use the presenter class shown in the previous section, to add a preview image and actions for the media item being viewed. This example also shows the addition of a related media items row, which appears below the details listing. 

public class MediaItemDetailsFragment extends DetailsFragment {
    private static final String TAG = "MediaItemDetailsFragment";
    private ArrayObjectAdapter mRowsAdapter;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        Log.i(TAG, "onCreate");
        super.onCreate(savedInstanceState);

        buildDetails();
    }

    private void buildDetails() {
        ClassPresenterSelector selector = new ClassPresenterSelector();
        // Attach your media item details presenter to the row presenter:
        DetailsOverviewRowPresenter rowPresenter =
            new DetailsOverviewRowPresenter(new DetailsDescriptionPresenter());

        selector.addClassPresenter(DetailsOverviewRow.class, rowPresenter);
        selector.addClassPresenter(ListRow.class,
                new ListRowPresenter());
        mRowsAdapter = new ArrayObjectAdapter(selector);

        Resources res = getActivity().getResources();
        DetailsOverviewRow detailsOverview = new DetailsOverviewRow(
                "Media Item Details");

        // Add images and action buttons to the details view
        detailsOverview.setImageDrawable(res.getDrawable(R.drawable.jelly_beans));
        detailsOverview.addAction(new Action(1, "Buy $9.99"));
        detailsOverview.addAction(new Action(2, "Rent $2.99"));
        mRowsAdapter.add(detailsOverview);

        // Add a Related items row
        ArrayObjectAdapter listRowAdapter = new ArrayObjectAdapter(
                new StringPresenter());
        listRowAdapter.add("Media Item 1");
        listRowAdapter.add("Media Item 2");
        listRowAdapter.add("Media Item 3");
        HeaderItem header = new HeaderItem(0, "Related Items", null);
        mRowsAdapter.add(new ListRow(header, listRowAdapter));

        setAdapter(mRowsAdapter);
    }
}

Create a Details Activity

Fragments such as the DetailsFragment must be contained within an activity in order to be used for display. Creating an activity for your details view, separate from the browse activity, enables you to invoke your details view using an Intent. This section explains how to build an activity to contain your implementation of the detail view for your media items.

Start creating the details activity by building a layout that references your implementation of the DetailsFragment: 

<!-- file: res/layout/details.xml -->

<fragment xmlns:android="http://schemas.android.com/apk/res/android"
    android:name="com.example.android.mediabrowser.MediaItemDetailsFragment"
    android:id="@+id/details_fragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
/>

Next, create an activity class that uses the layout shown in the previous code example: 

public class DetailsActivity extends Activity
{
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.details);
    }
}

Finally, add this new activity to the manifest. Remember to apply the Leanback theme to ensure that the user interface is consistent with the media browse activity: 

<application>
  ...

  <activity android:name=".DetailsActivity"
    android:exported="true"
    android:theme="@style/Theme.Leanback"/>

</application>

Define a Listener for Clicked Items

After you have implemented the DetailsFragment, modify your main media browsing view to move to your details view when a user clicks on a media item. In order to enable this behavior, add an OnItemViewClickedListener object to the BrowseFragment that fires an intent to start the item details activity.

The following example shows how to implement a listener to start the details view when a user clicks a media item in the main media browsing activity: 

public class BrowseMediaActivity extends Activity {
    ...

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        ...

        // create the media item rows
        buildRowsAdapter();

        // add a listener for selected items
        mBrowseFragment.OnItemViewClickedListener(
            new OnItemViewClickedListener() {
                @Override
                public void onItemClicked(Object item, Row row) {
                    System.out.println("Media Item clicked: " + item.toString());
                    Intent intent = new Intent(BrowseMediaActivity.this,
                            DetailsActivity.class);
                    // pass the item information
                    intent.getExtras().putLong("id", item.getId());
                    startActivity(intent);
                }
            });
    }
}
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